Various needle-less injection devices with different configurations for injecting a—typically drug-containing—fluid through or into the human skin are known in the art. The conventional devices have in common that the fluid is ejected through a very small outlet of an ampoule through application of high pressure, whereby the fluid attains a very high exit velocity which is required for penetrating the skin or entering the skin and hence for a needle-less subcutaneous or intradermal injection. Such injection devices include an ampoule with an ampoule body forming a chamber for receiving the fluid to be injected. An axially movable, sealingly guided ampoule piston is disposed inside the chamber. The distal end of the ampoule also has an outlet for the fluid to be injected. When used as indicated, the region of the ampoule surrounding the outlet defines the skin contact surface for the needle-less injection through or into the human skin.
DE 10 2004 007 257 A1 describes a needle-less injection device of the aforedescribed type wherein, in addition, an exterior shape of the distal surface of the ampoule forming the skin contact surface has a convex and essentially edge-free contour.
Injection devices employing needles have been used since many decades as an alternative to needle-less injection devices. Such injection devices have the following commonalities which are noteworthy for the intended use of the invention:    (i) an ampoule with an ampoule body forming a chamber is provided,    (ii) a movably and sealingly guided ampoule piston is disposed in the ampoule body, and    (iii) the outlet is arranged at the distal end of the ampoule, from where the fluid to be injected enters a needle and—depending on the penetration depth of the needle and the employed therapy, e.g., with intradermal, subcutaneous or intramuscular injection—is released in the patient's body.
Special embodiments of injection devices with needles are syringes with a so-called Luer connection which represents a standardized connection for injection syringes (or injection cannulae). In addition, a bayonet coupling for attaching the needle can also be provided (so-called Luer-lock syringe).
Presently, the two aforedescribed injection systems are used side-by-side; the attending physician/the medical facility providing treatment is therefore required to have both injection devices on hand, if a selection needs to be made between the two injection systems. When ampoules are prefilled at the manufacturer with a liquid drug, a decision must already be made, if these are to be configured for needle-less injection systems or for injection systems using needles.
This significantly increases material and manufacturing costs as well as inventory costs and the logistic complexity for providing both injection systems on-site.
DE 103 40 613 A1 describes a device for injecting a fluid, which can be used as a one-way syringe or—by removing certain components of the device at defined rated breakpoints—as an ampoule for a needle-less injector. However, the rated breakpoints are at risk of accidentally breaking during the needle injection. Moreover, the rated breakpoints also not sufficiently smooth to satisfy all the requirements for the needle-less injection.
U.S. Pat. No. 5,769,138 describes an adapter with Spike-attachment for a needle-less injector. The adapter and the injector each include coupling elements for securing the adapter on the injector. Additional sealing elements are provided on the adapter to prevent air from entering the chamber of the injector. U.S. Pat. No. 5,919,159 also describes an adapter with Spike-attachment for a needle-less injector.
Accordingly, there is still a great need for technical solutions which eliminate or at least alleviate the aforementioned disadvantages.